Carpal Tunnel Expansion by Palmarly Directed Forces to the Transverse Carpal Ligament

Abstract

This study investigated the expansion of the carpal tunnel resulting from the application of palmarly directed forces to the transverse carpal ligament (TCL) from inside the carpal tunnel. Ten fresh-frozen cadaveric hands were dissected to evacuate the carpal tunnel and thus to expose the TCL. A custom lever device was built to apply forces, ranging from 10 to 200 N, to the TCL. Without force application, the carpal tunnel area was 148.4 ± 36.8 mm2. The force application caused the TCL to form arches with an increase in cross-sectional areas of 33.3 ± 5.6 mm2 at 10 N and 48.7 ± 11.4 mm2 at 200 N, representing respective increases of 22.4% and 32.8% relative to the initial carpal tunnel area. The TCL length remained constant under the applied forces. It was found that the TCL arch formation was due to the narrowing of the arch width, which resulted from the migration of the bony insertion sites of the TCL. A geometrical model of the carpal tunnel was then developed to elucidate the relationships among the arch width, TCL length, arch height, and arch area. The model illustrated the effectiveness of carpal tunnel expansion by TCL elongation or arch width narrowing.

Morphological and positional changes of the carpal arch and median nerve during wrist compression

“…These structural changes are likely related to the soft tissue components of the carpal tunnel boundary which provides the carpal tunnel with some degree of compliance [8, 12–15]. Recent studies support that the cross-sectional area of the carpal tunnel can be increased by narrowing the carpal arch width (CAW), i.e., distance between the trapezium and hook of hamate [13, 14, 16, 17]. Geometric modeling [16] and in vitro [13, 16] studies have shown that CAW narrowing is associated with palmar bowing of the TCL which increases the height and cross-sectional area of the carpal arch.…”

In vivo tissue interaction between the transverse carpal ligament and finger flexor tendons

“…However, the findings of the current study indicate that the increase in TCL arch height with increased wrist flexion and finger loading was likely the result of a volarly directed force by the tendons to the TCL. The TCL arching mechanism by flexor tendons is also supported by a previous study demonstrating that the TCL arch height increases when a volarly directed force is applied to the TCL from within the carpal tunnel [23]. …”

Tensile properties of the transverse carpal ligament and carpal tunnel complex

“…This has all along been challenging to researchers investigating the biomechanical properties and role of the TCL from a computational (Guo et al, 2009;Li et al, 2009;Main et al, 2012) and experimental (Garcia-Elias et al, 1989;Tengrootenhuysen et al, 2009;Xiu et al, 2010) perspective. This paper describes the first approach taken towards determining tensile properties of the TCL using a commercial Maillon Rapide Delta.…”

“…This model used a custom lever device to apply known forces that generated TCL arches. In the study by Li et al (2009), a geometric model was also developed to clarify the relationships between the TCL width, CA width, CA height and CA area. The author's model is different but provides a useful approach designed to determine the tensile properties of the intact TCL.…”